Each year over 230,000 people survive moderate and severe traumatic brain injury (TBI). As a result, a large number of individuals with TBI endure life-long impairment and disability. Traditional neuroimaging techniques such as CT and MRI have demonstrated limited correlation with brain injury severity and cognitive functioning. Continued advances in neuroimaging, however, have provided researchers with an important opportunity to study the pathophysiology of brain dysfunction following TBI. The goal of this study is to apply FNIRS -- an innovative optical imaging technique that has recently been applied in studies of cerebral blood flow -- in the study of episodic memory (i.e., new learning) after TBI. FNIRS measures several physiological parameters related to cerebral blood flow, including measurements of changes in oxy- and deoxyhemoglobin, which are also the dependent variables of primary interest in FMRI. FNIRS is non-invasive, uses no ionizing radiation, and does not require the use of high-field magnetization or a large external scanner. Thus, it has many advantages over conventional imaging (i.e., SPECT, PET, FMRI) and has the unique advantage of being highly portable and virtually unaffected by subject movement. While FNIRS has shown promise in gauging changes in cerebral functioning during cognitive tasks performed by healthy individuals, it remains unstudied as a technique for investigating neurocognitive compromise after brain injury, such as the impairments observed in episodic memory. The purpose of this study is twofold (1) to validate the use of FNIRS in studying cognition after TBI, and (2) to use FNIRS to examine brain activity related to episodic memory that may differ between injured and non-injured individuals. The proposed study will address these areas by directly comparing changes in blood-flow related parameters within subjects and between groups using both FNIRS and FMRI during episodic memory task performance. This study will examine 15 individuals with a history of moderate to severe traumatic brain injury (within the previous 1 to 3 years), and 15 healthy controls. The present findings will serve as the basis for future investigations of cognition after TBI and may also hold the promise of providing a more accessible form of neuroimaging that is applicable to studying pharmacological and rehabilitation interventions.